All scripture references RSV unless otherwise noted.
Those who will go to heaven are those who are travelling the road that leads there. Jesus said there are two roads and only two roads; one leads to eternal life and one leads to eternal death, the second death. It is, of course, foolish to travel a road that leads East, hoping to go West, but many believe that one can walk the road that leads to hell and end up in heaven because their sins had at one time been forgiven.
Those that are travelling the straight and narrow path that leads to life may often fall off the path into a ditch, but falling does not constitute switching roads. Deliberate rebellion to God and a life of deliberate indulgence in sin constitutes switching roads, but falling into sin, or even being bound by a sin that one hates and longs to be freed from does not constitute switching roads.
God said in Ezekiel Chapter 18, verses 26-28, "When a righteous man turns away from his righteousness and commits iniquity, he shall die for it; for the iniquity which he has committed he shall die. Again, when a wicked man turns away from the wickedness he has committed and does what is lawful and right, he shall save his life. Because he considered and turned away from all the transgressions which he had committed, he shall surely live, he shall not die." So, to turn away from righteousness constitutes switching roads from the road that leads to life to the road that leads to death. Likewise, turning away from wickedness constitutes switching roads from the road that leads to death to the road that leads to life.
Many would say, "That’s Old Testament. That doesn’t apply to us under the New Testament." First of all, if you are going to throw out this principle simply because it is recorded in the Old Testament, you need to also throw out the principle found in Psalms 103:12, "As far as the east is from the west, so far does he remove our transgressions from us." Secondly, you must remember that the New Testament is found in the old. The New Testament simply expounds and enlarges on what is found in the old. Remember that the first century church didn’t have a "New Testament"; they just had the old plus a few letters, and remember that Jesus quoted from the law and the prophets to show that He was the Christ.
God’s principles don’t change for God doesn’t change, and therefor we find the eternal principles of the Gospel in the Old Testament. So, in this same passage of scripture in Ezekiel, we find grace and forgiveness in verse 22 where God said of the man who turns from his wickedness, "None of the transgressions which he has committed shall be remembered against him;…" An example of this is the thief on the cross who switched roads in the very last moments of his life, and found forgiveness and Christ’s promise of eternal life.
Verse 30 of this same chapter (Ez. 18) says, "Therefore I will judge you, O house of Israel, every one according to his ways, says the Lord God. Repent and turn from all your transgressions, lest iniquity be your ruin." I will judge you according to your ways. That word ways is a Hebrew word that means "a road (as trodden)…" In other words, God judges us by the road on which we are travelling, not by our having been cleansed of former sins. We find forgiveness and cleansing as we travel the road that leads to life, for 1 Jo. 1:7 says, "but if we walk in the light, as he is in the light, we have fellowship with one another, and the blood of Jesus his Son cleanses us from all sin." The tense of the verb "cleanses" indicates a present ongoing process and not a one time event, so being cleansed by His blood is conditional upon walking in the light, walking the road that leads to life.
Many have stated that when we trust Christ as savior, He forgives all of our sins, past, present, and future. I really have been unable to find that statement or even that principle in scripture. He certainly has the potential to forgive our future sins, for His sacrifice literally paid the debt for all of our sins, past, present, and future, but faith in Christ doesn’t apprehend forgiveness for future sins. If it did, it wouldn’t matter what a person did; they could never do anything to derail their right standing with God and their forgiven state in God’s eyes, once they had trusted Christ as savior. However, we know this is not true, for Jesus Himself taught that if you, after having been forgiven, do not forgive your brother his sins against you, the Father will not forgive your sins, but will deliver you to the torturers (Mat. 18:23-35). Mat. 6:15 says, "but if you do not forgive men their trespasses, neither will your Father forgive your trespasses."
So we see that the only way to apprehend forgiveness for the sin of unforgiveness is by repenting of that sin and forgiving one’s brother. Once again the scripture shows that the way to eternal life is just that: a way. It’s a road, not a doctrine or an event, even a life-changing event such as the new birth. The new birth only allows someone to see the road and the goal of the road, and brings one into right standing with God so that they may begin to travel this road. However, the beginning of a journey will not apprehend the goal of the journey if the way or the road that leads to the goal is abandoned.
So, we see that the road that leads to life, eternal life, is just that: a road. It’s a path or a way that leads to a specific destination called "life", just as the road that leads to death is a path or a way that leads to the destination "death". We see also from 1 John 1:7 that only those that are traveling this road that leads to life find forgiveness for their sins. Who then will enter heaven? Those who are traveling the road that leads there. Simple, isn’t it?